A polyphenylene ether resin has an excellent mechanical property, electrical property, and thermal resistance, and has an excellent dimensional stability, and therefore it is used in a broad range. However, a processing property of molding thereof by itself is inferior. In order to improve the processing property, the technique of compounding a polyamide therewith is proposed in JP-B-45-997. And at present, it has become a material which has many varied uses.
Recently, an alloy of a polyamide and a polyphenylene ether has been provided with electrical conductivity, and development thereof rapidly progresses for uses as an exterior material of an automobile (a fender, a door panel, etc.) which is possible to be electrostatically painted.
As a technique of providing an alloy of a polyamide and a polyphenylene ether with electrical conductivity, for instance, JP-A-2-201811 discloses a technique of decreasing a value of surface resistance by making a carbon black contained mainly in a polyamide phase. JP-A-4-300296 discloses a technique that a composition comprising a polyamide, a polyphenylene ether, and a carbon black has excellent volume resistivity, fluidity, thermal resistance, and impact strength.
JP-A-8-508534 and U.S. Pat. No. 5,643,502 disclose a composition having excellent impact strength and volume resistivity, by compounding an electrically conductive carbon fibril. And JP-A-8-48869 discloses that a composition having excellent impact strength and volume resistivity can be obtained by compounding an electrically conductive carbon black after compatibilizing a polyamide and a polyphenylene ether.
Further, JP-A-10-310695 discloses a composition having excellent Dart impact strength and electrical conductivity, by using plural polyamides and an electrically conductive carbon black. U.S. Pat. No. 6,221,283 discloses a technique wherein a composition having excellent electrical conductivity can be obtained by restricting the amount of a compatibilizer to that of a specified one.
WO 2001/36536 discloses a technique that a composition comprising a polyphenylene ether, a polyamide, a talc, and carbon has excellent electrical conductivity, fluidity, and unnotched Izod impact strength.
WO 2001/81473 filed by the same applicant as that of the present invention discloses a technique that by making an electrically conductive filler reside in a polyphenylene ether phase, electrical conductivity, fluidity, a composition excellent in a coefficient of linear expansion and impact strength, and suppressing of generation of fines caused by pelletizing is obtained.
Besides these, many applications such as JP-A-2001-302905, JP-A-2002-129023, JP-A-2002-146205, JP-A-2002-146206, JP-A-2002-194207, JP-A-2002-194093, etc. were filed.
However, the above-described techniques still have a problem that when electrical conductivity is improved to the level required in electrostatic painting, Dart impact strength at low temperatures becomes deteriorated, which is practically inferior.
When providing a resin composition with impact resistance, generally, an impact modifier is added. As an example thereof, JP-A-64-81852 and JP-A-2-58563 disclose that impact resistance is improved by compounding two types elastomer of an ABA type triblock copolymer and an AB type diblock copolymer. Further, JP-A-6-240130 discloses that molding processability, a mechanical property, and thermal resistance are improved by compounding plural block copolymers having different weight ratios of a block of a vinyl aromatic compound.
However, in these techniques, addition of electrical conductive filler is not considered. Actually, when the electrical conductive filler is added a composition, Dart impact strength at low temperatures is abruptly decreased and thus the resulting composition has no practical use.
As stated above, only a combination of conventional arts can not fully solve a problem that both electrical conductivity and Dart impact strength at low temperatures are improved at the same time, and therefore development of a new technique has been eagerly hoped for.